To increase productivity, agricultural vehicles, such as combines, are becoming larger, headers are becoming wider, and travel speeds are increasing during harvest. Additionally, harvesting operations in a large field often involve simultaneous harvesting and unloading of harvested crop material (sometimes referred to in the art as unloading “on the go”). Typically, the combine has an unloading system that includes an unloading tube containing a helical auger. The auger is deployed for unloading crop material from an on board grain tank into an accompanying receiving container, such as a tractor pulled cart, wagon, truck, trailer, or the like. Unloading tubes cover the grain as it is unloaded, minimizing grain loss that would otherwise occur if the grain were exposed to windy conditions and other elements. However unloading systems that utilize augers have been found to be slower than desired for many agricultural operations. Also, as a consequence of necessary spacing between the auger flight edges and the interior surface of the unloading tube, the crop material can be damaged therebetween.
Belt in tube conveyors can provide a superior alternative to auger type conveyors. The belts are lighter, less costly, can be operated at faster speeds than augers, and thus have higher discharge capacity. Belt in tube conveyors can also deliver the crop material in a more continuous manner with less vibration. In general, it has been found that conveying crop material using belts results in less crop damage than augers.
There are a number of operational challenges when using grain unloading systems, particularly when unloading on the go. One of the challenges is providing an unloading system with a suitable length. When unloading grain from an agricultural harvester on the go, the harvester and the truck moving alongside the harvester must maintain an adequate clearance or spacing between them. Larger headers on combines require the truck to be positioned a significant distance away from the combine to avoid collision between the truck and the header. In such cases, the unloading system must be very long to traverse the clearance space and reach the right location in the truck to properly unload crop material from the combine. Longer unloading systems pose a challenge because they add significant weight to the harvester and increase the vehicle footprint during transport. In addition, longer unloading systems are not required for every operation. For example, a harvester might be equipped with a large header for one crop, requiring a much longer unloading system, and subsequently be equipped with a much smaller header for a different crop. As the smaller header would require much less clearance, the longer unloading system would be unnecessary and possibly difficult to use.
Another challenge with longer unloading systems is the difficulty in bringing the discharge end to a centered position relative to a grain cart or trailer to receive the unloaded grain. Centering of the conveyor relative to the cart or trailer is necessary in order to get a full load of grain in the cart or trailer without spillage.
Still another challenge with unloading systems is adequately protecting grain as it exits the unloading system into a receptacle. Unless the length of the unloading system occupies the entire distance between the harvester and grain receptacle, there will be a gap or clearance between the discharge end of the conveyor and the grain receptacle. Grain that exits the unloading system and enters the gap will be unprotected from wind and other elements in mid-air. If the gap is relatively large, and discharged grain is subjected to winds, the grain can be blown away and lost. Large gaps also make it difficult to control and direct the stream of grain after it exits the unloading system. Moreover, if the end of the unloading system is spaced too far apart from the receptacle, any stoppage or deceleration of the unloading system can cause a significant volume of grain in mid-air to drop straight down or fall short of the receptacle, resulting in grain loss if there is nothing in place to receive the fallen grain.